Most vehicles in use today utilize internal combustion engines. The internal combustion engine generally operates optimally at high engine speeds. One result for this is that the internal combustion engine generates a significant amount of exhaust gases when operating at low engine speeds. To remedy this problem, vehicles that operate optimally in all conditions are being developed. The hybrid electric vehicle is an example of such a vehicle.
There are many different types of hybrid electric vehicles, but they generally combine the internal combustion engine of a conventional vehicle with the batteries and electric motor of an electric vehicle. The power of the engine and that of the electric motor are suitably used in the hybrid electric vehicle so that the engine operates in an engine speed region that realizes good fuel consumption rates and low emissions. That is, the hybrid electric vehicle realizes reductions in fuel consumption and exhaust gases compared to conventional vehicles.
In the hybrid electric vehicle, the engine is designed to discontinue operation under certain conditions (hereinafter referred to as “idle stop”). Fuel consumption is further reduced by such operation. Vehicle speed, engine temperature, the depressed state of the brake pedal, and the depressed state of the accelerator pedal are determined, and in the case where predetermined drive conditions (i.e., idle stop conditions) are satisfied, control is performed to effect idle stop.
In an engine control method for typical hybrid electric vehicles, idle stop is discontinued if shifting into the reverse R range is performed. However, since shifting into the reverse R range occurs briefly when changing the shift range from the drive D range to the park P range (or from the park P range to the drive D range), if idle stop is engaged during this process, it will then be disengaged. That is, since the reverse R range is between the park P and drive D ranges, idle stop is disengaged while performing shifting between these two ranges then again engaged. However, it is preferable that the idle stop state be maintained for various reasons including the fact that fuel is consumed with the abrupt disengagement of idle stop.